Search results for "particle physic"
showing 10 items of 6828 documents
Search for new physics in single-top-quark production with the ATLAS detector at the LHC
2018
Esta tesis presenta dos análisis dedicados a la búsqueda de nueva física en eventos de producción de quarks top únicos con datos recopilados por el detector ATLAS en el LHC. A pesar de su gran éxito, se cree que debe haber una teoría más general que subyace al Modelo Estándar de física de partículas que arroge luz a preguntas sin respuesta, como la asimetría de materia-antimateria del universo o la existencia de la Materia Oscura. Esta tesis cubre dos enfoques diferentes para abordar los dos temas anteriores. El objetivo del primer análisis es explorar la estructura del vértice Wtb a través de la medición de asimetrías angulares relacionadas con los observables de polarización del bosón W q…
Measurement of top-quark polarisation observables and a search for dark matter in single-top-quark production with the ATLAS detector at the LHC
2022
Esta tesis presenta dos análisis diferentes basados en los datos resultantes de colisiones protón-protón a una energía en el centro de masas de 13 TeV recolectados con el detector ATLAS del LHC, correspondientes a una luminosidad integrada de 139 fb$^{-1}$. El primer análisis presenta una medida de secciones eficaces diferenciales normalizadas del canal de producción de quarks top en solitario $t$-channel, donde el quark top se desintegra leptónicamente, como función de los tres ángulos de polarización del leptón para eventos con quarks top y quarks antitop tanto separadamente como de forma inclusiva. Estos observables son particularmente sensibles a efectos de nueva física en el vértice $t…
Neutrino physics from cosmological observables and oscillation experiments
2018
Aquesta tesi se centra en la física dels neutrins. En particular, se centra en l'estudi de les oscil·lacions de sabor, el paper dels neutrins relíquia en alguns escenaris cosmològics i la interacció entre aquests dos temes. Els neutrins es troben entre les partícules elementals més conegudes. Presenten comportaments interessants, com les seves oscil·lacions, i constitueixen un dels vincles entre les diferents àrees de la física. A través d'aquest document explotem la seva relació amb la cosmologia, amb especial èmfasi en l'Univers primerenc, encara que també parlem de projectes relacionats amb les últimes etapes de la història de l'Univers. En la primera part de la tesi presentem un ajustam…
Role of theN*(1535)resonance and theπ−p→KYamplitudes in the OZI forbiddenπN→ϕNreaction
2008
We study the $\ensuremath{\pi}N\ensuremath{\rightarrow}\ensuremath{\phi}N$ reaction close to the $\ensuremath{\phi}N$ threshold within the chiral unitary approach, by combining the ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\Sigma}}^{\ensuremath{-}},{\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{K}^{0}{\ensuremath{\Sigma}}^{0}$, and ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{K}^{0}\ensuremath{\Lambda}$ amplitudes with the coupling of \ensuremath{\phi} to the $K$ components of the final states of these reactions via quantum loops. We obtain good agreement with experiment when the dominant ${\ensuremath{\pi}}^{\ensuremath{…
Charged charmonium molecules
2010
We make use of a self-consistent quark-model based study of four-quark charmonium-like states to interpret recent charmonium experimental data. We conclude that there exists a ${D}^{*}{\overline{D}}^{*}$ meson-meson molecule with quantum numbers $({I}^{G}){J}^{PC}=({1}^{\ensuremath{-}}){2}^{++}$. Our study confirms the presence of charged charmonium-like resonances on the excited charmonium spectrum. We find support from recent experimental data by the Belle Collaboration [R. Mizuk et al. (Belle Collaboration), Phys. Rev. D 78, 072004 (2008)]. Confirmation of the experimental data by the Belle Collaboration and the determination of the quantum numbers of the new structures would help in dis…
High-statistics study of f0(1500) decay into π0π0
1995
Abstract A partial-wave analysis of the reaction p p →π 0 π 0 π 0 has been performed using a high-quality high-statistics data set of 712 000 events. In addition to the f0(975) and f0(1300), the scalar resonance with mass m = (1500 ± 15) MeV and width Γ = (120 ± 25) MeV is necessary to describe the data.
Regge phenomenology in π0 and η photoproduction
2017
The $\ensuremath{\gamma}N\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}N$ and $\ensuremath{\gamma}N\ensuremath{\rightarrow}\ensuremath{\eta}N$ reactions at photon beam energies above 4 GeV are investigated within Regge models. The models include $t$-channel exchanges of vector ($\ensuremath{\rho}$ and $\ensuremath{\omega}$) and axial-vector (${b}_{1}$ and ${h}_{1}$) mesons. Moreover, Regge cuts of $\ensuremath{\rho}\mathbb{P},\phantom{\rule{0.28em}{0ex}}\ensuremath{\rho}{f}_{2},\phantom{\rule{0.28em}{0ex}}\ensuremath{\omega}\mathbb{P}$, and $\ensuremath{\omega}{f}_{2}$ are investigated. A good description of differential cross sections and polarization observables at photon beam energies fr…
Measurement of the double-βdecay half-life ofNd150and search for neutrinoless decay modes with the NEMO-3 detector
2009
The half-life for double-{beta} decay of {sup 150}Nd has been measured by the NEMO-3 experiment at the Modane Underground Laboratory. Using 924.7 days of data recorded with 36.55 g of {sup 150}Nd, we measured the half-life for 2{nu}{beta}{beta} decay to be T{sub 1/2}{sup 2{nu}}=(9.11{sub -0.22}{sup +0.25}(stat.){+-}0.63(syst.))x10{sup 18} yr. The observed limit on the half-life for neutrinoless double-{beta} decay is found to be T{sub 1/2}{sup 0{nu}}>1.8x10{sup 22} yr at 90% confidence level. This translates into a limit on the effective Majorana neutrino mass of <4.0-6.3 eV if the nuclear deformation is taken into account. We also set limits on models involving Majoron emission, right-hand…
On a topological interpretation of electronic and vibrational molecular energies
1998
Abstract A relationship between Randic's connectivity index and various quantum mechanical parameters derived from the Huckel Molecular Orbital (HMO) approach is demonstrated. When applied to conjugated hydrocarbons, this index represents the measure of the global π electron molecular energy and, therefore, of the resonance energy. Moreover, the development of the procedure, allows the introduction of a new definition of the bond order which, in turn, makes possible a better prediction not only for bond lengths of naphtalene but also for the resonance integral and conjugation energy for butadiene. Also, a corrected value for the Randic index is deduced, which allows for the reduction of the…
Measurement of the Soft-Drop Jet Mass in pp Collisions at s=13 TeV with the ATLAS Detector
2018
Jet substructure observables have significantly extended the search program for physics beyond the standard model at the Large Hadron Collider. The state-of-the-art tools have been motivated by the ...